gold/target.h

   1 // target.h -- target support for gold   -*- C++ -*-
   2
   3 // The abstract class Target is the interface for target specific
   4 // support.  It defines abstract methods which each target must
   5 // implement.  Typically there will be one target per processor, but
   6 // in some cases it may be necessary to have subclasses.
   7
   8 // For speed and consistency we want to use inline functions to handle
   9 // relocation processing.  So besides implementations of the abstract
  10 // methods, each target is expected to define a template
  11 // specialization of the relocation functions.
  12
  13 #ifndef GOLD_TARGET_H
  14 #define GOLD_TARGET_H
  15
  16 #include <cassert>
  17
  18 #include "elfcpp.h"
  19
  20 namespace gold
  21 {
  22
  23 class General_options;
  24 class Object;
  25 template<int size, bool big_endian>
  26 class Sized_relobj;
  27 template<int size, bool big_endian>
  28 struct Relocate_info;
  29 class Symbol;
  30 template<int size>
  31 class Sized_symbol;
  32 class Symbol_table;
  33
  34 // The abstract class for target specific handling.
  35
  36 class Target
  37 {
  38  public:
  39   virtual ~Target()
  40   { }
  41
  42   // Return the bit size that this target implements.  This should
  43   // return 32 or 64.
  44   int
  45   get_size() const
  46   { return this->pti_->size; }
  47
  48   // Return whether this target is big-endian.
  49   bool
  50   is_big_endian() const
  51   { return this->pti_->is_big_endian; }
  52
  53   // Machine code to store in e_machine field of ELF header.
  54   elfcpp::EM
  55   machine_code() const
  56   { return this->pti_->machine_code; }
  57
  58   // Whether this target has a specific make_symbol function.
  59   bool
  60   has_make_symbol() const
  61   { return this->pti_->has_make_symbol; }
  62
  63   // Whether this target has a specific resolve function.
  64   bool
  65   has_resolve() const
  66   { return this->pti_->has_resolve; }
  67
  68   // Return the default address to use for the text segment.
  69   uint64_t
  70   text_segment_address() const
  71   { return this->pti_->text_segment_address; }
  72
  73   // Return the ABI specified page size.
  74   uint64_t
  75   abi_pagesize() const
  76   { return this->pti_->abi_pagesize; }
  77
  78   // Return the common page size used on actual systems.
  79   uint64_t
  80   common_pagesize() const
  81   { return this->pti_->common_pagesize; }
  82
  83  protected:
  84   // This struct holds the constant information for a child class.  We
  85   // use a struct to avoid the overhead of virtual function calls for
  86   // simple information.
  87   struct Target_info
  88   {
  89     // Address size (32 or 64).
  90     int size;
  91     // Whether the target is big endian.
  92     bool is_big_endian;
  93     // The code to store in the e_machine field of the ELF header.
  94     elfcpp::EM machine_code;
  95     // Whether this target has a specific make_symbol function.
  96     bool has_make_symbol;
  97     // Whether this target has a specific resolve function.
  98     bool has_resolve;
  99     // The default text segment address.
 100     uint64_t text_segment_address;
 101     // The ABI specified page size.
 102     uint64_t abi_pagesize;
 103     // The common page size used by actual implementations.
 104     uint64_t common_pagesize;
 105   };
 106
 107   Target(const Target_info* pti)
 108     : pti_(pti)
 109   { }
 110
 111  private:
 112   Target(const Target&);
 113   Target& operator=(const Target&);
 114
 115   // The target information.
 116   const Target_info* pti_;
 117 };
 118
 119 // The abstract class for a specific size and endianness of target.
 120 // Each actual target implementation class should derive from an
 121 // instantiation of Sized_target.
 122
 123 template<int size, bool big_endian>
 124 class Sized_target : public Target
 125 {
 126  public:
 127   // Make a new symbol table entry for the target.  This should be
 128   // overridden by a target which needs additional information in the
 129   // symbol table.  This will only be called if has_make_symbol()
 130   // returns true.
 131   virtual Sized_symbol<size>*
 132   make_symbol()
 133   { abort(); }
 134
 135   // Resolve a symbol for the target.  This should be overridden by a
 136   // target which needs to take special action.  TO is the
 137   // pre-existing symbol.  SYM is the new symbol, seen in OBJECT.
 138   // This will only be called if has_resolve() returns true.
 139   virtual void
 140   resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*)
 141   { abort(); }
 142
 143   // Scan the relocs for a section, and record any information
 144   // required for the symbol.  OPTIONS is the command line options.
 145   // SYMTAB is the symbol table.  OBJECT is the object in which the
 146   // section appears.  SH_TYPE is the type of the relocation section,
 147   // SHT_REL or SHT_RELA.  PRELOCS points to the relocation data.
 148   // RELOC_COUNT is the number of relocs.  LOCAL_SYMBOL_COUNT is the
 149   // number of local symbols.  PLOCAL_SYMBOLS points to the local
 150   // symbol data from OBJECT.  GLOBAL_SYMBOLS is the array of pointers
 151   // to the global symbol table from OBJECT.
 152   virtual void
 153   scan_relocs(const General_options& options,
 154               Symbol_table* symtab,
 155               Layout* layout,
 156               Sized_relobj<size, big_endian>* object,
 157               unsigned int sh_type,
 158               const unsigned char* prelocs,
 159               size_t reloc_count,
 160               size_t local_symbol_count,
 161               const unsigned char* plocal_symbols,
 162               Symbol** global_symbols) = 0;
 163
 164   // Relocate section data.  SH_TYPE is the type of the relocation
 165   // section, SHT_REL or SHT_RELA.  PRELOCS points to the relocation
 166   // information.  RELOC_COUNT is the number of relocs.  VIEW is a
 167   // view into the output file holding the section contents,
 168   // VIEW_ADDRESS is the virtual address of the view, and VIEW_SIZE is
 169   // the size of the view.
 170   virtual void
 171   relocate_section(const Relocate_info<size, big_endian>*,
 172                    unsigned int sh_type,
 173                    const unsigned char* prelocs,
 174                    size_t reloc_count,
 175                    unsigned char* view,
 176                    typename elfcpp::Elf_types<size>::Elf_Addr view_address,
 177                    off_t view_size) = 0;
 178
 179  protected:
 180   Sized_target(const Target::Target_info* pti)
 181     : Target(pti)
 182   {
 183     assert(pti->size == size);
 184     assert(pti->is_big_endian ? big_endian : !big_endian);
 185   }
 186 };
 187
 188 } // End namespace gold.
 189
 190 #endif // !defined(GOLD_TARGET_H)